Vehicle seat unit

ABSTRACT

The invention is intended to improve operability of a seat unit in a process of turning it from an approximately horizontal storage position to a seating position. An upper end of a seatback (SB) in its seating position and a rear end of a seat cushion (SC) are joined together by a string ( 23 ), and two helical springs (biasing members) are provided at a forward portion of the seat cushion (SC). The first helical spring ( 39 ) exerts an upward biasing force which is smaller than the weight of the seat cushion (SC) against the seat cushion (SC), while the second helical spring ( 38 ) exerts an upward biasing force which is larger than the weight of the seat cushion (SC) against the seat cushion (SC). With this arrangement, a rear portion of the seat cushion (SC) is lifted when the seat is turned from the seating position to the storage position, and a small force is needed for lifting the seat cushion (SC) when it is turned in a reverse direction. The seat unit can be brought to the seating position by a single action since the seatback (SB) and the seat cushion (SC) are joined to each other by the string ( 23 ).

TECHNICAL FIELD

This invention relates to a seat unit for a vehicle.

BACKGROUND ART

A vehicle seat unit of the prior art is found in Japanese UnexaminedPatent Publication No. 2002-96663. FIG. 7 shows the vehicle seat unitdisclosed in this Unexamined Patent Publication No. 2002-96663, in whichFIG. 7A shows a condition that enables an occupant to be seated, FIG. 7Bshows a condition where a seat cushion 90 has been swung to an uprightposition by lifting its rear end, and FIG. 7C shows a condition wherethe rear end of the seat cushion 90 has been turned frontward from thecondition of FIG. 7B down to an approximately horizontal position and,after sliding seat rails rearward, a seatback 91 has been turnedfrontward (to a reversed position).

Specifically, when a lever 92 of a lock mechanism provided in theseatback 91 is operated in the condition of FIG. 7A, a cable 93 ispulled, a latch (not shown) provided at the seat bottom to fix the seatcushion 90 in position is disengaged from a striker 94 and, then, therear end of the seat cushion 90 is turned upward by a spring (not shown)provided at a seat front bracket 95. Subsequently, the seat cushion 90is turned frontward down to the approximately horizontal position withthe aid of its own weight according to the Publication.

However, the seat cushion 90 is normally considerably heavy as itincorporates a frame unit (not shown) to prevent deformation of the seatcushion 90 and to give a comfortable ride. For this reason, it isnecessary to exert a great force when turning the seat cushion 90 fromits reversed position shown in FIG. 7C to the position of FIG. 7B (asshown by an arrow) in the construction of the aforementioned UnexaminedPatent Publication No. 2002-96663, resulting in poor operability.Operability is further worsened by two-step operation involving the needto turn up the seatback 91 and then the seat cushion 90.

In light of the foregoing, it is an object of the invention to reducethe amount of force needed for turning a seat cushion from itsapproximately horizontal position to a position where an occupant can beseated on a seat unit by operating the seat cushion, thereby achievingan improvement in operability.

DISCLOSURE OF THE INVENTION

A seat unit for a vehicle according to a first construction of theinvention includes a seat cushion which can take either a seatingposition where its cushion face is directed upward to allow an occupantto be seated or a reversed position where the cushion face is directeddownward with a forward end of the seat cushion in its seating positionsupported by a pivot of a support member to make the seat cushionswingable, a seatback which can take either an upright position where itis set to an approximately vertical position or a forwardly turnedposition where it is turned frontward with a lower end of the seatbackin its upright position supported by a pivot of a support member to makethe seatback swingable, and a biasing member for exerting an upwardbiasing force against a rear end of the seat cushion when it is in thereversed position.

According to the first construction of the invention, the seat can takeeither the seating position where the occupant is allowed to be seatedor the reversed position where the cushion face of the seat cushion isdirected downward such that luggage or the like can be placed. Thisconstruction not only offers enhanced convenience of the vehicle but,with the provision of the biasing member for exerting an upward biasingforce against a forward portion of the seat cushion in its reversedposition, reduces the amount of force needed for lifting the seatcushion from its reversed position, thereby achieving an improvement inoperability.

A seat unit for a vehicle according to a second construction of theinvention is characterized in that the biasing member exerts its biasingforce only when the seat cushion is between the reversed position and anapproximately vertical position.

According to the second construction of the invention, the biasingmember exerts its biasing force only when the seat cushion is betweenthe reversed position and the approximately vertical position, so thatit is possible to reduce the amount of force needed for lifting the seatcushion from its reversed position. In addition, since the biasingmember exerts only an extremely small biasing force or no biasing forceat all when the seat cushion is in its approximately vertical position,it is possible to prevent the seat cushion from falling down with impacttoward the seating position due to the biasing force. This means thatthe biasing member exerts its biasing force only when the seat cushionis lifted from the reversed position where the largest force is needed.This offers a further improvement in operability.

A seat unit for a vehicle according to a third construction of theinvention is characterized in that the biasing member exerts its upwardbiasing force when the seat cushion turns from the approximatelyvertical position to the reversed position by its own weight, the upwardbiasing force being smaller than a downward-directed force produced bythe weight of the seat cushion.

According to the third construction of the invention, the biasing memberexerts its upward biasing force when the seat cushion turns from theapproximately vertical position to the reversed position by its ownweight, the upward biasing force being smaller than thedownward-directed force produced by the weight of the seat cushion. Thisconstruction serves to prevent the seat cushion from falling down to thereversed position with impact when it is turned from the approximatelyvertical position to the reversed position. In addition, theconstruction serves to prevent the seat cushion from rising by itselffrom the reversed position.

A seat unit for a vehicle according to a fourth construction of theinvention is characterized by further including an interlock device bywhich the seat cushion is lifted in interlocked action with the seatbackwhen the seatback is lifted from the forwardly turned position to theupright position.

According to the fourth construction of the invention, the seatback ismade such that it can take either the approximately vertical positionwhere the occupant is allowed to be seated or the forwardly turnedposition where luggage or the like can be placed, thereby offeringenhanced convenience of the vehicle. Particularly when the reversedposition of the seat cushion explained with reference to theaforementioned first construction and the forwardly turned position ofthe seatback are combined, a portion of the seat unit can be used as aluggage platform, so that the convenience of the vehicle is dramaticallyenhanced.

Furthermore, according to the fourth construction of the invention, theseat unit is provided with the interlock device by which the seatcushion is lifted in interlocked action with the seatback when theseatback is lifted from the forwardly turned position to the uprightposition. This construction serves to offer extremely good operability,since ordinary two-step operation involving the need to individuallylift up the seatback and the seat cushion can be performed by a singleaction.

A seat unit for a vehicle according to a fifth construction of theinvention is characterized in that the interlock device includes aflexible tie member interconnecting the rear end of the seat cushion andan upper end of the seatback.

According to the fifth construction of the invention, the tie memberinterconnects the rear end of the seat cushion, or the forward end ofthe seat cushion in its seating position, and the upper end of theseatback, or a forward end of the seatback in its forwardly turnedposition, so that the forward end of the seat cushion is lifted ininterlocked action with the seatback when the seatback is swung up.Thus, the fifth construction offers good operability. Furthermore,because the tie member is a flexible member, operation is easy, and theseat set to the seating position does not interfere with sitting actionof the occupant, whereas the seat converted to a luggage platform whereluggage can be placed does not interfere with loading and unloading ofthe luggage.

A seat unit for a vehicle according to a sixth construction of theinvention is characterized by further including a second biasing memberfor exerting an upward biasing force against a rear portion of the seatcushion when it is in the seating position.

According to the sixth construction of the invention, the seat unit isprovided with the second biasing member for exerting an upward biasingforce against the rear portion of the seat cushion when it is in theseating position. This construction serves to reduce the amount of forceneeded for lifting the seat cushion from its seating position, oreliminate the need to manually lift the seat cushion up to a specificangle, thereby achieving an improvement in operability.

A seat unit for a vehicle according to a seventh construction of theinvention is characterized in that the second biasing member exerts itsbiasing force only when the seat cushion is between the seating positionand the approximately vertical position.

According to the seventh construction of the invention, the secondbiasing member exerts its biasing force only when the seat cushion isbetween the seating position and the approximately vertical position.This construction serves to reduce the amount of force needed forlifting the seat cushion from its seating position and prevent the seatcushion from falling beyond the approximately vertical position down tothe reversed position with impact when it is lifted from the seatingposition to the approximately vertical position.

A seat unit for a vehicle according to an eighth construction of theinvention is characterized in that the second biasing member exerts itsbiasing force in such a way that the seat cushion is swung up by aspecific angle which is smaller than a right angle, and the seat unitfurther includes a lock mechanism for holding the seat cushion in theseating position and an unlock mechanism for unlocking the lockmechanism.

According to the eighth construction of the invention, the secondbiasing member exerts its biasing force in such a way that the seatcushion is swung up by a specific angle which is smaller than a rightangle, so that this construction exhibits those effects which have beenexplained with reference to the aforementioned sixth or seventhconstruction to a greater extent. In addition, the provision of the lockmechanism for holding the seat cushion in the seating position and theunlock mechanism for unlocking the lock mechanism serves to prevent theseat cushion from rising by itself due to the biasing force of thesecond biasing member when the seat cushion is in the seating positionand the occupant is not seated. Furthermore, the seat cushion rises fromthe seating position up to a specific position immediately when the lockmechanism has been unlocked. This ensures smooth and easy operation whenturning the seat cushion from the seating position to the reversedposition through the vertical position.

A seat unit for a vehicle according to a ninth construction of theinvention includes a seat cushion which can take either a seatingposition where its cushion face is directed upward to allow an occupantto be seated or a reversed position where the cushion face is directeddownward with a forward end of the seat cushion in its seating positionsupported by a pivot of a support member to make the seat cushionswingable, a seatback which can take either an upright position where itis set to an approximately vertical position or a forwardly turnedposition where it is turned frontward with a lower end of the seatbackin its upright position supported by a pivot of a support member to makethe seatback swingable, and an interlock device by which the seatcushion is lifted in interlocked action with the seatback when theseatback is lifted from the forwardly turned position to the uprightposition.

According to the ninth construction of the invention, the seat unitincludes the seat cushion which can take either the seating position orthe reversed position and the seatback which can take either the uprightposition or the forwardly turned position. The seat unit thusconstructed is highly convenient serving a seating function for seatingthe occupant as well as a platform function for loading luggage.Furthermore, the seat cushion is lifted from the reversed position ininterlocked action with the seatback when the seatback is lifted fromthe forwardly turned position. This serves to offer extremely goodoperability, since ordinary two-step operation involving the need toindividually lift up the seatback and the seat cushion can be performedby a single action.

A seat unit for a vehicle according to a tenth construction of theinvention is characterized in that the interlock device includes aflexible tie member interconnecting a rear end of the seat cushion andan upper end of the seatback.

According to the tenth construction of the invention, the tie memberinterconnects the rear end of the seat cushion, or a forward end of theseat cushion in its seating position, and the upper end of the seatback,or a forward end of the seatback in its forwardly turned position, sothat the forward end of the seat cushion is lifted in interlocked actionwith the seatback when the seatback is swung up as explained inconnection with the aforementioned ninth construction. Thus, the tenthconstruction offers good operability. Furthermore, because the tiemember is a flexible member, operation is easy, and the seat set to theseating position does not interfere with sitting action of the occupant,whereas the seat converted to a luggage platform where luggage can beplaced does not interfere with loading and unloading of the luggage.

A seat unit for a vehicle according to an eleventh construction of theinvention is characterized by further including a base member supportingthe seat cushion and the seatback, and a slide mechanism supporting thebase member in such a manner that the base member can be slid betweenits seating position and a storage position located behind the seatingposition along a longitudinal direction of the vehicle.

According to the eleventh construction of the invention, the seat unitis provided with the base member which is made sidable between theseating position and the storage position located behind the seatingposition along the longitudinal direction of the vehicle, so that theoccupant can easily vary the seating position according to his or herpreference to make the seat unit comfortable to sit in. When convertingthe seat unit to the luggage platform by turning the seat cushion to thereversed position and the seatback to the forwardly turned position, itis possible to make a sufficient working space to do so in thelongitudinal direction by sliding the base member up to the storageposition located behind the seating position. In addition, another seatunit located in front of the aforesaid seat unit can also be slidrearward to provide comfortable sitting and improved ride quality.

As so far described, the present invention makes it possible to reducethe amount of force needed for lifting the seat cushion in order to turnthe seat unit from its approximately horizontal storage position to theseating position by operating the seatback and the seat cushion. Theinvention also enables an improvement in work efficiency andoperability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view of a seat unit according to the invention;

FIG. 2 is a view showing components of a slide rail mechanism of theseat unit according to the invention;

FIG. 3 is a diagram showing a seat cushion lock mechanism;

FIGS. 4A through 4F are diagrams showing operating procedures forturning the seat unit between a seating position and a reversedposition;

FIG. 5 is a diagram showing the arrangement and structure of helicalsprings;

FIGS. 6A through 6E are diagrams showing the functions of the helicalsprings; and

FIGS. 7A through 7C show a prior art example.

BEST MODE FOR CARRYING OUT THE INVENTION

A specific embodiment of the invention is now described with referenceto the drawings.

FIG. 1 is a diagram generally showing a seat unit according to theinvention as it is set in a condition where a seat cushion SC of afoldable seat S for a vehicle is set to its reversed position and aseatback SB is set to its forwardly turned position, and FIG. 2 is aview showing components of a slide rail mechanism. In the followingdescription of the embodiment, the condition in which the seat cushionSC is set to the reversed position and the seatback SB is set to theforwardly turned position is referred to as a “storage position,” and acondition in which an occupant can be seated, that is, the seat cushionSC is set to an approximately horizontal position with its cushion facedirected upward, and the seatback SB is set to an approximately verticalupright position is referred to as a “seating position.”

As shown in FIGS. 1 and 2, the seat cushion SC is swingably attached toforward portions of a pair of left and right upper slide rails 6 viarespective turn mechanisms 8, while the seatback SB is attached to rearportions of the upper slide rails 6 via a pair of left and right hingemechanisms 10 in a manner that the seatback SB can be turned down. Theleft and right upper slide rails 6 are mounted on respective lower sliderails 12 which are fixed to the floor of the vehicle body so that theupper slide rails 6 can slide back and forth in the longitudinaldirection of the vehicle. The upper slide rails 6 and the lower sliderails 12 together constitute a seat slide mechanism. Provided on theoutside of the seat slide mechanism is a side member 14 which is fixedto the floor of the vehicle body.

A seat cushion frame (not shown) is installed inside the seat cushion SCand latches 16 respectively having latch grooves 16 a (refer to FIG. 3showing a seat cushion lock mechanism) are joined to rear left and rightside portions of the seat cushion frame in such a fashion that thelatches 16 protrude downward from the bottom of the seat cushion SC asit is held in an approximately horizontal seating position. Forks 20mounted on shafts are affixed to the respective latches 16. The forks 20serve as locking members which fit on respective strikers 18, with alocking groove 20 a formed in each fork 20.

Also installed inside the seat cushion SC is a fork manipulator 22, andthe left and right forks 20 mounted on the shafts are affixed to bothends of the fork manipulator 22. The fork manipulator 22 has a generallyU-shaped handgrip 24 slightly projecting rearward from a rear face ofthe seat cushion SC and an unlocking strap 25 connected to the handgrip24. When the unlocking strap 25 is pulled rearward (in a direction shownby arrow B), the forks 20 turn in a direction shown by arrow C and, as aconsequence, they are unlocked from the strikers 18.

The slide mechanism for the seat S is now described in great detailreferring to FIG. 2. While FIG. 2 shows only a left-hand slide railmechanism as viewed by an occupant seated in a frontward-lookingposition, left and right slide rail mechanisms basically have aleft-right symmetrical construction. A bracket 28L for supporting thebottom of the seat cushion SC and holding a lock plate 26 movably up anddown is joined to a top surface of the upper slide rail 6 whichconstitutes part of the seat slide mechanism, a pair of left and rightbrackets 28L, 28R (refer to FIG. 1) being joined to each other by meansof a connecting member 30 extending in the direction of the vehiclewidth.

A lower end portion of a lock plate support 32L is fixed to a forwardend portion of the left-hand bracket 28L and a seat cushion support 34Lserving as a pivot bar is connected to a forward end portion of the seatcushion frame. Provided on the inside of the seat cushion support 34L isa helical spring 38 serving as a seat cushion biasing member which willbe described later in detail with reference to FIGS. 5 and 6.

The side member 14 includes a lower member 54 having an approximatelyU-shaped cross section and fixed to the floor of the vehicle body and anupper member 56 joined to the lower member 54. There are provided tworectangular openings 56 a, 56 b formed in a forward portion of the uppermember 56, and the striker 18 of which both ends are fixed to two facingside walls of the lower member 54 is provided in a rear portion of thelower member 54. The striker 18 is so arranged that it can lock theaforementioned latch 16 through a rectangular opening 28 a formed in thebracket 28L.

When the seat S is set to the seating position, or when the seat cushionSC is in its approximately horizontal position before being turned toits upright position, a locking claw 26 a of the lock plate 26 is fittedin the rectangular opening 56 a. When the seat cushion SC is turnedupward, the locking claw 26 a is caused to ascend by an unillustratedspring mechanism and becomes released from the rectangular opening 56 ato a free position. As a result, the seat S becomes slidable back andforth. When the seat S is slid backward and the seat cushion SC is setto its reversed position, the locking claw 26 a fits in the rectangularopening 56 b, thereby preventing the seat S set in the reversed positionfrom freely sliding back and forth.

Next, movements of the seat S as it is turned from the seating positionto the storage position, and vice versa, are explained referring to FIG.4. FIG. 4A shows the movement of the seat S as it is turned from theseating position to the storage position, and FIG. 4B shows the movementof the seat S as it is returned from the storage position to the seatingposition. Broken lines in these Figures indicate positions taken by theseat S before it is moved while solid lines indicate positions taken bythe seat S after it has been moved.

In a step shown in FIG. 4A, when the unlocking strap 25 of the seat S ispulled rearward as it is in the seating position, the seat cushion SC isreleased from its locked state as explained earlier with reference toFIG. 1. At this point, the seat cushion SC stops at a position swung upas shown by a black arrow. (A lift mechanism for producing this swing-upaction includes a helical spring (second biasing member) serving as abiasing member which will be described later.) In step shown in FIG. 4B,the seat cushion SC is turned frontward from this position slightlybeyond the vertical position and, then, the seat S is moved rearwardalong the floor F of the vehicle body (in a direction shown by a hatchedarrow) together with the brackets 28 with the aid of the seat slidemechanism.

An upper end of the seatback SB and a rear end of the seat cushion SCare joined together by a string 23 so that the seat cushion SC does notturn frontward by its own weight at this point in time.

Next, in step shown in FIG. 4C, when the seatback SB is turned frontwardwhile manipulating a lever from an approximately horizontal position L1to an upper position L2 as shown by an arrow for turning the seatback SBfrontward, the seat S is brought to the storage position wherelarge-sized luggage or the like can be placed on the seat S, in whichthe seat S is approximately horizontal with the seatback SB set to theforwardly turned position and the seat cushion SC set to the reversedposition.

On the other hand, to bring the seat S from the storage position back tothe seating position (as shown in FIG. 4D to 4F), the seatback SB isfirst lifted while holding a handgrip P provided at an upper rearportion of the seatback SB in step shown in FIG. 4D. Since the seatcushion SC is linked to the seatback SB by the string 23, the rear endof the seat cushion SC suspended by the seatback SB is also lifted atthe same time.

Since another helical spring (first biasing member) for applying anupward force is provided at a forward position where the seat cushion SCis swung down, it is possible to lift the seat cushion SC without theneed to exert a great force. (This helical spring (first biasing member)will be described later.) Operation of step shown in FIG. 4D is finishedwhen the seatback SB has been brought back to an upright position whichis its specified original position. When returned to the uprightposition, the seatback SB is locked into the specified position whereits swing motion is prohibited. Since the seat cushion SC is linked tothe seatback SB by the string 23, the seat cushion SC does not return toits reversed position even if it is slightly tilted frontward.

Next, in step shown in FIG. 4E, the seat S is pushed frontward as shownby a hatched arrow to bring it back to its specified position. Then, instep shown in FIG. 4F, the seat cushion SC is returned to itsapproximately horizontal position, or the seating position, by pullingthe string 23 rearward. At this point, the latches 16 provided on thebottom of the seat cushion SC fit on the strikers 18 and the seat S isset to the locked state.

The aforementioned helical springs (the first biasing member and thesecond biasing member are hereinafter referred to as the first helicalspring and the second helical spring, respectively) are described indetail referring to FIG. 5 showing their arrangement and structure andFIG. 6 showing their functions, respectively.

Referring to FIG. 5, the two helical springs, i.e., the first helicalspring 39 and the second helical spring 38, are provided at lower frontpositions of the seat cushion SC. First, the arrangement and structureof the first helical spring 39 are described. As viewed by the occupantseated in the frontward-looking position, a pin 34 b extending inwardand a circular hole 34 d are provided at a front portion of a seatcushion support 34R which is provided at a forward right-hand cornerportion of the seat cushion SC, and a lock plate support 32R is providedon the outside of the seat cushion support 34R. The lock plate support32R is provided with a fixing pin 32 b of which end is notched to formtwo-split prongs extending inward. The fixing pin 32 b is inserted intothe circular hole 34 d in the seat cushion support 34R and, then, acentral part 39 c of the first helical spring 39 is fixed to the splitend of the fixing pin 32 b. The pin 34 b of the seat cushion support 34Ris made such that it can catch a hooking part 39 a of the first helicalspring 39 formed by bending its extreme outer end portion into agenerally U-shape only when the seat cushion SC is between anapproximately vertical position and the reversed position.

On the other hand, the second helical spring 38 having a larger biasingforce than the first helical spring is provided at a forward left sideof the seat cushion SC as viewed by the occupant seated in thefrontward-looking position. Specifically, a pin 34 a extending inwardand a circular hole 34 c are provided at a front portion of the seatcushion support 34L which is provided at a forward left-hand cornerportion of the seat cushion SC, and the lock plate support 32L isprovided on the outside of the seat cushion support 34L. The lock platesupport 32L is provided with a fixing pin 32 a of which end is notchedto form two-split prongs extending inward. The fixing pin 32 a isinserted into the circular hole 34 c in the seat cushion support 34Land, then, a central part 38 c of the second helical spring 38 is fixedto the split end of the fixing pin 32 a. The pin 34 a of the seatcushion support 34L is made such that it can catch a hooking part 38 aof the second helical spring 38 formed by bending its extreme outer endportion into a generally U-shape only when the seat cushion SC isbetween the seating position and a position where it is swung up byapproximately 30 degrees.

This means that the first helical spring 39 exerts an upward biasingforce only when the seat cushion SC is between the approximatelyvertical position and the reversed position, whereas the second helicalspring 38 exerts an upward biasing force only when the seat cushion SCis between the seating position and the position where it is swung up byapproximately 30 degrees.

This is further explained referring to FIG. 6, in which “left side” isthe side where the second helical spring 38 is provided and “right side”is the side where the first helical spring 39 is provided, and both the“left side” and “right side” are views as seen from outside to inside.FIG. 6A shows a condition where the seat cushion SC (not shown) is inthe seating position. In this condition, the hooking part 38 a of thesecond helical spring 38 catches on the pin 34 a and the second helicalspring 38 exerts its biasing force to lift up a rear portion of the seatcushion support 34L which is connected to the seat cushion SC.

When the latches 16 are unlocked from the strikers 18 as describedearlier, the rear end of the seat cushion SC is lifted by the biasingforce of the second helical spring 38 up to a position shown in FIG. 6B.The position of FIG. 6B shows a condition where a balance is maintainedbetween the weight of the seat cushion SC and the biasing force of thesecond helical spring 38 and the seat cushion SC is held stationary atan angle between the horizontal and 30 degrees.

FIG. 6C shows a condition where the seat cushion SC has been swung up toan approximately vertical position. In this condition, the hooking part38 a of the second helical spring 38 is set apart from the pin 34 a, sothat the seat cushion SC can be easily moved as no biasing force isexerted on it. Needless to say, the second helical spring 38 exerts nobiasing force even when the seat cushion SC is turned frontward to itsreversed position. Although not illustrated, no biasing force is exertedon the right side where the first helical spring 39 is provided when theseat cushion SC is in the approximately vertical position, because thehooking part 39 a of the first helical spring 39 is separated from thepin 34 b in this condition.

When the seat cushion SC is turned further frontward, the right sideprovided with the first helical spring 39 is brought to a position shownin FIG. 6D. At the position of FIG. 6D, the hooking part 39 a of thefirst helical spring 39 is already caught by the pin 34 b. In thisembodiment, the first helical spring 39 has a smaller biasing force thanthe second helical spring 38 that is not large enough to support theweight of the seat cushion SC. Therefore, the seat cushion SC does notstay stationary at the position shown in FIG. 6D but is automaticallybrought to a completely reversed position shown in FIG. 6E whenreleased. Since the first helical spring 39 exerts the upward biasingforce against the seat cushion SC, however, the seat cushion SC isprevented from dropping with impact.

Although the first helical spring 39 exerts the upward biasing forceagainst the seat cushion SC in its reversed position shown in FIG. 6E,the seat cushion SC is held in the approximately horizontal positionbecause the first helical spring 39 does not produce a sufficientbiasing force to lift the seat cushion SC upward overcoming its weight.

When the seat cushion SC is turned in an opposite direction from itsreversed position shown in FIG. 6E to its approximately verticalposition via the position shown in FIG. 6D, the first helical spring 39exerts the upward biasing force on the seat cushion SC as previouslyexplained with reference to FIG. 4. This allows an operator to easilylift the seat cushion SC.

As thus far described, in turning the seat S including the seatback SBand the seat cushion SC from the seating position to the approximatelyhorizontal storage position to allow storage of luggage or the like, therear end of the seat cushion SC is lifted by a specific angle by thebiasing force exerted by the second helical spring 38 which serves as abiasing member provided at the forward portion of the seat cushion SCwhen the seatback SB is unlocked, and when the seatback SB and the seatcushion SC are turned to their reversed positions through approximatelyvertical positions, the seat cushion SC is prevented from dropping withimpact to the reversed position by the biasing force exerted by thefirst helical spring 39 which serves as a biasing member also providedat the forward portion of the seat cushion SC according to the presentinvention. When the seat cushion SC has been set to the reversedposition, it is allowed to remain in the approximately horizontalposition because the first helical spring 39 does not have a sufficientbiasing force to lift the seat cushion SC upward overcoming its weight.

When turning the seat S from the storage position to the seatingposition, it is possible to bring the seat cushion SC together with theseatback SB back to the upright position by just lifting the seatbackSB. This is because a forward end portion of the seatback SB in itsforwardly turned position (that is, the upper end of the seatback SB inthe seating position) and a forward end portion of the seat cushion SCin its reversed position (that is, the rear end of the seat cushion SCin the seating position) are interconnected by the string 23 as if beingbridged thereby. Furthermore, this operation can be performed withoutthe need to exert a great force due to the upward biasing force of thefirst helical spring 39 provided at the seat cushion SC.

1. A seat unit for a vehicle comprising: a seat cushion having a forwardend thereof pivotably supported by a support member, enabling the seatcushion to move between a seating position where a cushion face of theseat cushion is directed upward to allow an occupant to be seated and areversed position where the cushion face is directed downward; aseatback having a lower end thereof pivotably supported by a supportmember, enabling the seatback to move between an upright position wherethe seatback is set to an approximately vertical position and aforwardly turned position where the seatback is turned frontward; and aninterlock device by which said seat cushion is lifted in interlockedaction with said seatback when said seatback is lifted from theforwardly turned position to the upright position; wherein saidinterlock device includes a flexible tie member interconnecting a rearend of said seat cushion and an upper end of said seatback.
 2. The seatunit for a vehicle according to claim 1, further comprising: a basemember supporting said seat cushion and said seatback; and a slidablemechanism supporting said base member in such a manner that said basemember can be slid between a seating position and a storage positionlocated behind the seating position along a longitudinal direction ofthe vehicle.
 3. A seat unit for a vehicle comprising: a seat cushionhaving a forward end and a rear end, said forward end being pivotablysupported by a support member, enabling the seat cushion to move betweena seating position where a cushion face of said seating cushion isdirected upward to allow an occupant to be seated and a reversedposition where the cushion face is directed downward passing through anapproximately vertical position; a seatback having a lower end in anupright position and pivotably supported by a support member, enablingthe seatback to move between said upright position where said seatbackis in an approximately vertical position and a forwardly turned positionwhere said seatback is turned frontward; and a biasing member forexerting an upward biasing force to the rear end of said seat cushionwhen said seat cushion turns from the approximately vertical position ofsaid seat cushion to the reversed position, said upward biasing forcebeing smaller than a downward-directed force produced by a weight ofsaid seat cushion; and an interlock device interlocking said seatcushion and said seatback such that said seat cushion is lifted ininterlocked action with said seatback when said seatback is lifted fromthe forwardly turned position to the upright position.
 4. A seat unitfor a vehicle comprising: a seat cushion having a forward end and a rearend, said forward end being pivotably supported by a support member,enabling the seat cushion to move between a seating position where acushion face of said seating cushion is directed upward to allow anoccupant to be seated and a reversed position where the cushion face isdirected downward passing though an approximately vertical position; aseatback having a lower end in an upright position and pivotablysupported by a support member, enabling the seatback to move betweensaid upright position where said seatback is in an approximatelyvertical position and a forwardly turned position where said seatback isturned frontward; a biasing member for exerting an upward biasing forceto the rear end of said seat cushion when said seat back is in thereversed position; and an interlock device interlocking said seatcushion and said seatback such that said seat cushion is lifted ininterlocked action with said seatback when said seatback is lifted fromthe forwardly turned position to the upright position.
 5. The seat unitfor a vehicle according to claim 4, wherein said interlock deviceincludes a flexible tie member interconnecting the rear end of said seatcushion and an upper end of said seatback.
 6. The seat unit for avehicle according to claim 5, further comprising a second biasing memberfor exerting an upward biasing force to the rear portion of said seatcushion when it is in the seating position.
 7. The seat unit for avehicle according to claim 6, wherein said second biasing member exertsits biasing force only when said seat cushion turns from the seatingposition to the approximately vertical position.
 8. The seat unit for avehicle according to claim 7, wherein said second biasing member exertsthe biasing force in such a way that said seat cushion is swung upwardlyby a specific angle which is smaller than a right angle, said seat unitfurther comprising a lock mechanism for holding said seat cushion in theseating position and an unlock mechanism for unlocking the lockmechanism.
 9. A seat unit for a vehicle comprising: a seat cushionhaving a forward end and a rear end, said forward end being pivotablysupported by a support member, enabling the seat cushion to move betweena seating position where a cushion face of said seating cushion isdirected upward to allow an occupant to be seated and a reversedposition where the cushion face is directed downward passing through anapproximately vertical position; a seatback having a lower end in anupright position and pivotably supported by a support member, enablingthe seatback to move between said upright position where said seatbackis in an approximately vertical position and a forwardly turned positionwhere said seatback is turned frontward; a biasing member for exertingan upward biasing force to the rear end of said seat cushion when saidseat cushion is in the reversed position; and a second biasing memberfor exerting an upward biasing force to a rear portion of said seatcushion when it is in the seating position.
 10. A seat unit for avehicle comprising: a seat cushion having a forward end and a rear end,said forward end being pivotably supported by a support member, enablingthe seat cushion to move between a seating position where a cushion faceof said seating cushion is directed upward to allow an occupant to beseated and a reversed position where the cushion face is directeddownward passing through an approximately vertical position; a seatbackhaving a lower end in an upright position and pivotably supported by asupport member, enabling the seatback to move between said uprightposition where said seatback is in an approximately vertical positionand a forwardly turned position where said seatback is turned frontward;a biasing member for exerting an upward biasing force to the rear end ofsaid seat cushion when said seat cushion is in the reversed position; abase member supporting said seat cushion and said seatback; and a slidemechanism supporting said base member in such a manner that said basemember can be slid between a seating position and a storage positionlocated behind the seating position along a longitudinal direction ofthe vehicle.
 11. A seat unit for a vehicle comprising: a seat cushionhaving a forward end and a rear end, said forward end being pivotablysupported by a support member, enabling the seat cushion to move betweena seating position where a cushion face of said seating cushion isdirected upward to allow an occupant to be seated and a reversedposition where the cushion face is directed downward passing through anapproximately vertical position; a seatback having a lower end in anupright position and pivotably supported by a support member, enablingthe seatback to move between said upright position where said seatbackis in an approximately vertical position and a forwardly turned positionwhere said seatback is turned frontward; a lock mechanism for lockingthe seat cushion in said seating position; an unlock mechanism forunlocking a locked state of the seat cushion by the lock mechanism; abiasing member for exerting an upward biasing force to the rear end ofsaid seat cushion in said seating position such that the seat cushion isswung upward from the seating position, upon release from the lockedstate by said unlock mechanism, to a predetermined angle that is lessthan a vertical position and said seat cushion is free from said biasingforce when the seat cushion is in an angle range between an anglegreater than said predetermined angle and an angle past said verticalposition where the rear end of the seat cushion turns forward past saidvertical position; an interlock device for preventing the seat cushionfrom further turning in a forward direction when the seatback is in theupright position; and a lever member, mounted on the seatback, whichallows, upon operation, said seatback in the upright position to swingforward; wherein said seat cushion, said seatback, and said interlockdevice are positioned such that said interlock device allows said seatcushion in, the forwardly turned position past said vertical position,to swing further forward by its own weight when the seatback isforwardly turned upon operation of the lever member and said interlockdevice pulls said seat cushion, which was maintained in the reversedposition, upward to an angle position before said vertical position byturning said seatback from the forwardly turned position to the uprightposition.